Caliper brake apparatus

ABSTRACT

A caliper brake apparatus includes a brake lining that advances/retreats relative to a caliper main body supported on a vehicle body and can apply a frictional force by slidingly contacting a disc, an anchor pin that supports a guide plate supporting the brake lining on the caliper main body such that it can freely advance/retreat, a piston that advances/retreats relative to the caliper main body and can press the brake lining via the guide plate, a diaphragm that abuts a rear surface of the piston and defines a pressure chamber within the caliper main body and elastically deforms due to pressure of compressed air within the pressure chamber so as to move the piston, and a piston plate that supports the piston on the anchor pin such that the piston can freely slide. The piston includes a plurality of thermal insulation members whose distal ends protrude toward the guide plate.

TECHNICAL FIELD

The present invention relates to a caliper brake apparatus that appliesfrictional force to a disc that rotates together with a wheel to brakethe rotation of the wheel.

BACKGROUND ART

Conventionally, in a vehicle such as a rail car, a hydrostatic pressurebrake apparatus that performs braking by utilizing hydrostatic pressuresuch as hydraulic or pneumatic pressure has been used. JP2011-236958Adiscloses a caliper brake apparatus in which a piston thatadvances/retreats due to deformation of a pressing elastic film inaccordance with changes in fluid pressure presses a brake lining againsta disc.

SUMMARY OF INVENTION

However, in the caliper brake apparatus disclosed in JP2011-236958A, thepiston is fastened by a plurality of bolts to a guide plate to which thebrake lining is attached. Thus, frictional heat generated by contactbetween the brake lining and the disc may be transferred from the guideplate to the pressing elastic film via the piston.

The present invention was created in consideration of theabove-described problem, and an object thereof is to improve the thermalinsulation of frictional heat generated by contact between the brakelining and the disc.

According to one aspect of this invention, a caliper brake apparatusthat is configured to sandwich a disc which rotates together with awheel to apply a frictional force thereto, includes: a caliper main bodythat is supported on a vehicle body, a brake lining that is configuredto advance/retreat relative to the caliper main body and can apply africtional force by slidingly contacting the disc, a guide plate thatsupports the brake lining, an anchor pin that supports the guide plateon the caliper main body such that it can freely advance/retreat, apiston that is configured to advances/retreats relative to the calipermain body and can press against the brake lining via the guide plate, anelastic film that abuts a rear surface of the piston and defines apressure chamber within the caliper main body and elastically deformsdue to pressure of a working fluid within the pressure chamber so as tomove the piston, and a piston plate that supports the piston on theanchor pin such that the piston can freely slide. The piston includes aplurality of small pistons provided such that their distal ends protrudetoward the guide plate.

The details as well as other features and advantages of this inventionare set forth in the remainder of the specification and are shown in theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a caliper brake apparatus according to anembodiment of the present invention;

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a cross-section view along line III-III in FIG. 2;

FIG. 4A is a front view of a piston and a piston plate;

FIG. 4B is a cross-section view along line IVB-IVB in FIG. 4A;

FIG. 5A is a front view of an alternative embodiment of the piston andthe piston plate;

FIG. 5B is a cross-section view along line VB-VB in FIG. 5A;

FIG. 6 is a cross-section view of a side surface of a caliper brakeapparatus according to another alternative embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS

A caliper brake apparatus 100 according to an embodiment of the presentinvention will now be explained below referring to the drawings.

First, referring to FIGS. 1 and 2, the overall constitution of thecaliper brake apparatus 100 will be explained.

The caliper brake apparatus 100 is a pneumatic brake for a rail car inwhich compressed air is used as the working fluid. The caliper brakeapparatus 100 includes a caliper main body 10 that is supported on abogie (vehicle body) (not illustrated) via a support frame 20, a pair ofbrake linings 7 that can apply frictional force by advancing/retreatingrelative to the caliper main body 10 to slidingly contact a disc 6, aguide plate 8 that supports a brake lining 7, a pair of anchor pins 43that support the guide plate 8 on the caliper main body 10 such that itcan freely advance/retreat, and a pressing mechanism 50 that presses thebrake lining 7 against the disc 6 by pressure of compressed air.

The caliper brake apparatus 100 sandwiches the disc 6 which rotatestogether with a wheel 5 to apply a frictional force thereto.Specifically, the caliper brake apparatus 100 grips the disc 6 from bothsurfaces thereof with the pair of brake linings 7 to brake the rotationof the wheel 5 by the frictional force between the disc 6 and the brakelinings 7.

The disc 6 is formed on the front and back surfaces of the wheel 5 androtates integrally with the wheel 5. Instead of a constitution in whichthe disc 6 is formed integrally with the wheel 5, a separate disc 6 thatrotates together with the wheel 5 can be provided.

As shown in FIG. 1, the caliper main body 10 includes a first caliperarm 12 and a second caliper arm 14 that extend so as to straddle thedisc 6, a yolk 13 that connects the first caliper arm 12 and the secondcaliper arm 14, and a pair of brackets 15 for supporting the calipermain body 10 on the bogie.

As shown in FIG. 2, the caliper main body 10 is floatingly supportedsuch that it can slide relative to the support frame 20 by an upperslide pin 30 and a lower slide pin 32. Thereby, the caliper main body 10follows the relative movement in the axial direction of the wheel 5relative to the bogie, and the brake linings 7 oppose the disc 6 of thewheel 5 in parallel.

The upper slide pin 30 and the lower slide pin 32 are provided so as topenetrate the support frame 20. Both ends of the upper slide pin 30 andthe lower slide pin 32 are respectively connected to the brackets 15 ofthe caliper main body 10. The caliper main body 10 is supported on thesupport frame 20 so as to enable relative movement in the axialdirection of the upper slide pin 30 and the lower slide pin 32. As shownin FIG. 1, the exposed parts of the upper slide pin 30 and the lowerslide pin 32 are covered by rubber boots 34 so that they are protectedfrom dust and the like.

The brake linings 7 receive a pressing force generated by the pressingmechanism 50 and are pressed to abut the disc 6 in parallel. The brakelinings 7 each have a brake block 9 that abuts the disc 6 which rotatestogether with the wheel 5. A rear surface that is opposite to thesurface of the brake lining 7 on which the brake block 9 is provided isfixed to the guide plate 8. The brake linings 7 brake the rotation ofthe wheel 5 by the frictional force generated by contact between thebrake blocks 9 and the disc 6.

The guide plate 8 has a dovetail groove 8 a that is formed along thelengthwise direction and in which the rear surface of the brake lining 7engages. Both ends in the lengthwise direction of the guide plate 8 aresupported on the caliper main body 10 by the pair of anchor pins 43.Adjusters 40 which include the anchor pins 43 will be explained indetail below with reference to FIG. 3.

Next, the internal structure of the caliper main body 10 will beexplained referring to FIGS. 3, 4A, and 4B.

As shown in FIG. 3, the caliper main body 10 is provided with a pair ofadjusters 40 arranged on both ends in the lengthwise direction and thepressing mechanism 50 arranged between the pair of adjusters 40.

The adjusters 40 adjust the initial position of the brake lining 7relative to the disc 6. The adjusters 40 are respectively fastened tothe top and bottom ends of the caliper main body 10 by the anchor bolts42.

The adjusters 40 each include a brake lining receiver 41 fixed to thecaliper main body 10 by the anchor bolt 42, an anchor pin 43 that isprovided such that it can advance/retreat relative to the brake liningreceiver 41 and supports the brake lining 7 on the caliper main body 10,a return spring 44 that biases the brake lining 7 in a direction awayfrom the disc 6, and a gap adjustment mechanism 45 that adjusts the gapbetween the brake lining 7 and the disc 6 to a fixed amount whenreleasing the braking.

The anchor pins 43 are formed in an approximately closed-end cylindricalshape. The anchor pins 43 are provided in a pair so as to support bothends of the brake lining 7. The anchor pins 43 each have a collar part43 b that engages with the guide plate 8. The anchor pins 43 are eachprovided such that a bottom part 43 a protrudes from the brake liningreceiver 41, and support the brake lining 7 by fitting the collar parts43 b into both ends of the guide plate 8.

When the brake lining 7 approaches the disc 6, the anchor pins 43 arewithdrawn from the brake lining receivers 41 by the guide plate 8 thatdisplaces together with the brake lining 7 so as to become displaced inthe axial direction. During braking in which the brake lining 7slidingly contacts the disc 6, the anchor pins 43 support the brakelining 7 so as to counteract the disc 6 which is attempting to move thebrake lining 7 in the circumferential direction by frictional force.

On the inner periphery of each anchor pin 43, the return spring 44 andthe gap adjustment mechanism 45 are mounted. A sliding part that isexposed to the outside during sliding in each anchor pin 43 is coveredby a rubber boot 47 so that it is protected from dust and the like.

Each return spring 44 is a coil spring that is compressed and interposedin the inner periphery of each anchor pin 43. When changing from abraking state to a non-braking state, the collar part 43 b of the anchorpin 43 pushes back the brake lining 7 via the guide plate 8 by thebiasing force of the return spring 44 so as to separate the brake lining7 from the disc 6 by a predetermined distance. Thereby, the distancebetween the brake lining 7 and the disc 6 when releasing the braking canbe adjusted and the heat dissipation of the disc 6 can be improved.

The gap adjustment mechanisms 45 make adjustments such that the amountby which the brake lining 7 is returned by the biasing force of thereturn springs 44 when releasing the braking is always constant. Inother words, the gap adjustment mechanisms 45 maintain the intervalbetween the brake lining 7 and the disc 6 such that it is alwaysconstant when releasing the braking.

The pressing mechanism 50 includes a cylinder 51 formed on the calipermain body 10, a piston 52 that advances/retreats relative to thecylinder 51 and can press the brake lining 7 via the guide plate 8, adiaphragm 53 that abuts a rear surface 52 c of the piston 52 and definesa pressure chamber 55 within the caliper main body 10 and serves as anelastic film that elastically deforms due to pressure of compressed airwithin the pressure chamber 55 so as to move the piston 52, and a pistonplate 58 that supports the piston 52 on the anchor pins 43 such that thepiston 52 can freely slide.

The pressing mechanism 50 deforms the diaphragm 53 by adjusting the airpressure in the pressure chamber 55, and causes the piston 52 toadvance/retreat relative to the cylinder 51 by deforming the diaphragm53. The pressing mechanism 50 presses the brake lining 7 against thedisc 6 via the guide plate 8 by causing the piston 52 to retreat fromthe cylinder 51.

The cylinder 51 includes a cylinder main body 51 a whose inner peripherythe piston 52 advances toward/retreats from, and a caliper cover 54 thatsandwiches the diaphragm 53 between itself and the cylinder main body 51a to fix it and blocks the rear surface of the cylinder main body 51 ato define the pressure chamber 55.

The cylinder main body 51 a is formed in an oval cylinder shape so as tosurround the periphery of the piston 52 in an annular shape. On theinner periphery of the cylinder main body 51 a, a dust seal 51 b isprovided to slidingly contact the outer peripheral surface of the piston52 and protect it from dust and the like.

The caliper cover 54 is a plate member that is formed in an oval shapecorresponding to the cylinder main body 51 a. The caliper cover 54 isfixed to the end surface of the cylinder main body 51 a with a pluralityof bolts 54 a.

The diaphragm 53 elastically deforms by the pressure within the pressurechamber 55 to move the piston 52. The diaphragm 53 includes a peripheraledge part 53 a that forms the outermost periphery, a pressing part 53 cthat is formed on the innermost periphery, and a bellows part 53 b thatis formed continuously between the peripheral edge part 53 a and thepressing part 53 c.

The peripheral edge part 53 a is sandwiched and fixed between thecylinder main body 51 a and the caliper cover 54. At this time, theperipheral edge part 53 a serves as packing, and thus the air tightnessof the pressure chamber 55 is secured.

The bellows part 53 b is positioned between the inner peripheral surfaceof the cylinder main body 51 a and the outer peripheral surface of thepiston 52. The bellows part 53 b extends from a folded state (the statein FIG. 3) when the pressure in the pressure chamber 55 rises, andreturns to a folded state when the pressure in the pressure chamber 55drops. In other words, the bellows part 53 b can deform between a foldedstate and an extended state by the air pressure that is supplied to thepressure chamber 55.

The pressing part 53 c abuts the piston 52, and is displaced in theretreating direction of the piston 52 by the extension of the bellowspart 53 b which was folded. The piston 52 is pressed by the displacementof the pressing part 53 c and moves within the cylinder 51.

The pressure chamber 55 is defined by the diaphragm 53 and the calipercover 54 inside the cylinder 51. The pressure chamber 55 causes thepiston 52 to advance/retreat in accordance with theexpansion/contraction of the volume of the pressure chamber 55. Athrough-hole 56 (refer to FIG. 2) is provided on the pressure chamber55. Condensed air for deforming the diaphragm 53 during braking issupplied through the through-hole 56 from an external air pressuresource.

The piston 52 abuts the rear surface of the guide plate 8. The piston 52is retained within the cylinder 51 by the diaphragm 53.

As shown in FIGS. 4A and 4B, the piston 52 includes a piston main body52 a that is formed in an elliptical shape, and thermal insulationmembers 59 consisting of a plurality of small pistons that are providedsuch that their distal ends protrude from a front surface 52 b towardthe guide plate 8.

The piston main body 52 a includes the front surface 52 b that faces theguide plate 8 and the rear surface 52 c that is formed on the oppositeside of the front surface 52 b and abuts the diaphragm 53. The pistonmain body 52 a is formed integrally with and supported on the pistonplate 58.

The piston 52 advances/retreats within the cylinder 51 by thedeformation of the diaphragm 53 that abuts the rear surface 52 c of thepiston main body 52 a. In this way, the diaphragm 53 presses against theentire surface of the rear surface 52 c that is formed in an ellipticalshape, and thus the pressing efficiency can be improved compared to acase in which the thermal insulation members 59 are directly pressed.

The thermal insulation members 59 suppress the transfer of frictionalheat generated by contact between the brake lining 7 and the disc 6 tothe diaphragm 53 via the piston main body 52 a. In the presentembodiment, 21 thermal insulation members 59 are provided.

Each thermal insulation member 59 is formed in a cylindrical shape, andits base part is embedded and fixed in the piston main body 52 a.Instead of embedding the thermal insulation members 59 into the pistonmain body 52 a, they can also be fixed by attaching them to the frontsurface 52 b of the piston main body 52 a or the like. By fixing thethermal insulation members 59 to the piston main body 52 a, the thermalinsulation members 59 do not tilt when pressed, and thus the pressingefficiency can be improved.

The thermal insulation members 59 are formed with a material having lowthermal conductivity compared to the piston main body 52 a. By providingthe thermal insulation members 59, the transfer of frictional heatgenerated by contact between the brake lining 7 and the disc 6 to thepiston 52 can be suppressed.

Also, since a plurality of the thermal insulation members 59 abut theguide plate 8, the surface area in which a pressing force generated bydeformation of the diaphragm 53 can be transferred increases, and theability of the brake lining 7 to follow the deformation of the disc 6caused by frictional heat or the like can be improved.

As shown in FIGS. 5A and 5B, two thermal insulation members 59 having alarge diameter can also be provided. In this way, any number of thermalinsulation members 59 can be provided as long as the number is more thanone.

As shown in FIG. 3, the piston plate 58 is a plate member provided inparallel to the guide plate 8. The piston plate 58 is provided such thatits end surface is flush with the front surface 52 b of the piston mainbody 52 a.

The piston plate 58 displaces together with the piston 52 to move inparallel relative to the guide plate 8. The piston plate 58 approachesthe guide plate 8 during braking, and separates from the guide plate 8when releasing the braking. The piston plate 58 is formed integrallywith the piston 52. However, the piston plate 58 can be formedseparately from the piston 52, and the piston 52 can be used by fixingit to the piston plate 58.

The piston plate 58 includes a pair of sliding holes 58 a into which theanchor pins 43 are inserted on both ends thereof in the lengthwisedirection. The piston plate 58 is provided to engage with the anchorpins 43 which are inserted into the sliding holes 58 a so that it canfreely slide in the axial direction of the anchor pins 43. The pistonplate 58 sets the position of the piston 52 within the cylinder 51 bythe engagement of the sliding holes 58 a on both ends thereof with theanchor pins 43.

The sliding hole 58 a at the top side among the pair of sliding holes 58a is formed in a circular hole shape, and the other sliding hole 58 a atthe bottom side is formed in a notch shape. Thereby, the piston plate 58can be attached to the caliper main body 10 by inserting one anchor pin43 into the top-side sliding hole 58 a, and then fitting the otheranchor pin 43 from the bottom into the bottom-side sliding hole 58 a.Therefore, the attachability of the piston plate 58 to the caliper mainbody 10 can be improved.

In a braking state in which the piston 52 presses the brake lining 7, agap 57 is formed between the guide plate 8 and the piston plate 58. Dueto the formation of this gap 57, frictional heat generated by contactbetween the brake lining 7 and the disc 6 is prevented from beingdirectly transferred to the piston plate 58 from the guide plate 8.

Next, the action of the caliper brake apparatus 100 will be explainedreferring mainly to FIG. 3.

When the rail car is travelling, the wheel 5 rotates at high speed.Herein, when the caliper brake apparatus 100 is switched to a brakingstate by the operation of a driver or the like, compressed air suppliedfrom an air pressure source is sent into the pressure chamber 55 via thethrough-hole 56 to deform the diaphragm 53. When the diaphragm 53deforms, the bellows part 53 b of the diaphragm 53 extends, and thepressing part 53 c causes the piston 52 to slide in the direction of thedisc 6.

The pressing part 53 c of the diaphragm 53 displaces in the direction ofthe wheel 5, and presses the brake lining 7 against the disc 6 that isprovided on the wheel 5 via the piston 52. When a frictional force isgenerated upon contact between the disc 6 and the brake lining 7 that ispressed by the diaphragm 53, the rotation of the wheel 5 is braked.Thereby, the speed of the rail car is decreased and the rail careventually comes to a stop.

At this time, the piston 52 abuts the guide plate 8 via the thermalinsulation members 59 whose distal ends protrude from the front surface52 b. Therefore, the transfer of frictional heat generated by contactbetween the brake lining 7 and the disc 6 to the piston 52, or in otherwords the transfer of such heat to the diaphragm 53, is suppressed.

Also, when the caliper brake apparatus 100 is switched to a brakingstate, thermal deformation of the disc 6 occurs due to the frictionalheat between the disc 6 and the brake lining 7. However, since thepiston 52 includes a plurality of thermal insulation members 59, thepiston 52 can press against the brake lining 7 with a uniform pressingforce following the thermal deformation of the disc 6. Thus, it ispossible to achieve stable braking.

When braking of the wheel 5 by the caliper brake apparatus 100 isreleased by the operation of a driver or the like, the brake lining 7separates from the state in which it was abutting the disc 6 due to therestoring force of the return springs 44 provided within the adjusters40. Further, compressed air within the pressure chamber 55 is dischargedfrom the through-hole 56, the bellows part 53 b of the diaphragm 53returns to the folded shape it was in before braking, and the pressingpart 53 c returns to the position it was in before braking. Thereby, thepiston 52 also returns to the position it was in before braking.

Thereby, the disc 6 and the brake lining 7 are made to oppose each otheragain with a constant interval therebetween by the gap adjustmentmechanisms 45. Therefore, the wheel 5 becomes able to rotate without anyinfluence from the caliper brake apparatus 100.

At this time, the piston 52 is pulled farther away from the disc 6 dueto inertial force along with the separation of the guide plate 8 fromthe disc 6 due to the restoring force of the return springs 44.Therefore, when the caliper brake apparatus 100 enters a non-brakingstate from a braking state, an air space can be formed between the guideplate 8 and the thermal insulation members 59, i.e. between the guideplate 8 and the piston 52. Thus, the thermal insulation of frictionalheat generated by contact between the brake lining 7 and the disc 6 canbe improved, and the diaphragm 53 can be protected from high heat.

As in the alternative embodiment shown in FIG. 6, disc springs 60 can beprovided in the gap 57 between the guide plate 8 and the piston plate 58as biasing members that bias the piston plate 58 so that it separatesfrom the guide plate 8 when releasing the braking.

The disc springs 60 are formed in an annular shape corresponding to theouter peripheral shape of the anchor pins 43. The disc springs 60 arefitted to the outer periphery of the anchor pins 43 for use. Instead ofthe disc springs 60, coil springs or the like can also be used as thebiasing members.

In this case, when releasing the braking of the caliper brake apparatus100, the disc springs 60 force the piston plate 58 to separate from theguide plate 8 by the biasing force thereof. Thus, the air space formedbetween the guide plate 8 and the piston 52 can be enlarged.Accordingly, the thermal insulation of frictional heat generated bycontact between the brake lining 7 and the disc 6 can be furtherimproved.

The biasing force of the disc springs 60 is set to be smaller than thebiasing force of the return springs 44. Therefore, at the start ofbraking in the caliper brake apparatus 100, first, the disc springs 60are compressed and the thermal insulation members 59 of the piston 52abut the guide plate 8. Subsequently, when the piston 52 strokesfurther, the return springs 44 are compressed and the brake lining 7abuts the disc 6.

On the other hand, when releasing the braking of the caliper brakeapparatus 100, first, the return springs 44 return to their lengthbefore the start of braking, and the brake lining 7 separates from thedisc 6. Subsequently, the disc springs 60 return to their length beforethe start of braking, and the piston plate 58 is separated from theguide plate 8.

According to the above-described embodiments, the following effects areachieved.

The guide plate 8 that supports the brake lining 7 and the piston plate58 that supports the piston 52 are formed separately. The guide plate 8is supported by the anchor pins 43 to advance and retreat, and thepiston plate 58 is supported by the anchor pins 43 such that it canfreely slide. Therefore, when entering a non-braking state from abraking state, an air space can be formed between the guide plate 8 andthe piston 52. Thus, the thermal insulation of frictional heat generatedby contact between the brake lining 7 and the disc 6 can be improved,and the diaphragm 53 can be protected from high heat.

Further, when the caliper brake apparatus 100 is switched to a brakingstate, thermal deformation of the disc 6 occurs due to the frictionalheat between the disc 6 and the brake lining 7. However, since thepiston 52 includes a plurality of thermal insulation members 59, thepiston 52 can press against the brake lining 7 with a uniform pressingforce following the thermal deformation of the disc 6. Thus, it ispossible to achieve stable braking.

Embodiments of this invention were described above, but the aboveembodiments are merely examples of applications of this invention, andthe technical scope of this invention is not limited to the specificconstitutions of the above embodiments.

This application claims priority based on Japanese Patent ApplicationNo. 2012-022693 filed with the Japan Patent Office on Feb. 6, 2012, theentire contents of which are incorporated into this specification.

The embodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A caliper brake apparatus that is configured to sandwich a disc whichrotates together with a wheel to apply a frictional force thereto,comprising: a caliper main body that is supported on a vehicle body; abrake lining that is configured to advance/retreat relative to thecaliper main body and can apply a frictional force by slidinglycontacting the disc; a guide plate that supports the brake lining; ananchor pin that supports the guide plate on the caliper main body suchthat it can freely advance/retreat; a piston that is configured toadvances/retreats relative to the caliper main body and can pressagainst the brake lining via the guide plate; an elastic film that abutsa rear surface of the piston and defines a pressure chamber within thecaliper main body and elastically deforms due to pressure of a workingfluid within the pressure chamber so as to move the piston; and a pistonplate that supports the piston on the anchor pin such that the pistoncan freely slide, wherein the piston includes a plurality of smallpistons provided such that their distal ends protrude toward the guideplate.
 2. The caliper brake apparatus according to claim 1, wherein thepiston has a piston main body that is supported on the piston plate, anda base part of each small piston is embedded and fixed in the pistonmain body.
 3. The caliper brake apparatus according to claim 1, whereinthe small pistons are thermal insulation members that suppress heattransfer from the brake lining to the elastic film.
 4. The caliper brakeapparatus according to claim 1, wherein the piston plate has a slidinghole into which the anchor pin is inserted, and the piston plate isconfigured to slide in the axial direction of the anchor pin to moveparallel relative to the guide plate.
 5. The caliper brake apparatusaccording to claim 4, wherein the anchor pin is provided as a pair ofanchor pins so as to support both ends of the brake lining, and thesliding hole is provided as a pair of sliding holes on both ends of thepiston plate, such that the anchor pins are respectively inserted intothe sliding holes.
 6. The caliper brake apparatus according to claim 1,wherein the piston plate is formed integrally with the piston.
 7. Thecaliper brake apparatus according to claim 1, wherein a gap is formedbetween the guide plate and the piston plate in a braking state in whichthe piston presses against the brake lining.
 8. The caliper brakeapparatus according to claim 7, wherein a biasing member that biases thepiston plate so that it separates from the guide plate when the brakingis released is provided in the gap.
 9. The caliper brake apparatusaccording to claim 8, further comprising a return spring that pushesback the brake lining via the guide plate when the braking is releasedto separate the brake lining from the disc, wherein the biasing force ofthe biasing member is set to be smaller than the biasing force of thereturn spring.
 10. The caliper brake apparatus according to claim 8,wherein the biasing member is a disc spring that is formed in an annularshape corresponding to an outer peripheral shape of the anchor pin andfits on the outer periphery of the anchor pin.